Focal length adjustment apparatus with improved vibration and impact-resistance properties

Abstract

Disclosed herein is a focal length adjustment apparatus in which a magnetic fluid that serves as attenuation means is injected between a magnet and a coil to achieve an improvement in a magnetic flux density and damping effect. The apparatus comprises a moving unit including a lens barrel that contains at least one lens therein, and a coil arranged on an outer circumference of the lens barrel, a fixed unit including a yoke formed with an opening for receiving the lens barrel, a case into which the yoke is inserted and mounted, and a magnet affixed to the yoke to be arranged adjacent to the coil, a supporting member used to elastically support the moving unit relative to the case, and attenuation means interposed between the coil and the magnet to attenuate vibration of the moving unit.

Description

RELATED APPLICATIONS [0001] The present application is based on, and claims priority from, Korean Application Number 2005-003269, filed Jan. 13, 2005, the disclosure of which is incorporated by reference herein in its entirety. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a focal length adjustment apparatus using a voice coil motor (VCM), and more particularly, to a focal length adjustment apparatus in which a magnetic fluid that serves as attenuation means is injected between a magnet and a coil to achieve an improvement in a magnetic flux density and damping effect, whereby the strength of an electromagnetic force produced between the magnet and the coil can be enhanced and an impact-resistance property, a reliability in the adjustment of a focal length, and responsiveness can be improved. [0004] 2. Description of the Related Art [0005] In general, a camera includes a plurality of lenses, and is designed to adjust an optical ...

AI Technical Summary

Benefits of technology

[0021] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a focal length adjustment apparatus in which a magnetic fluid is injected between a magnet and a coil to achieve an improvement in a magnetic flux density and damping effect, whereby the strength of an electromagnetic force produced between the magnet and the coil can be enhanced and an impact-resistance property, a reliability in the adjustment of a focal length, and responsiveness can be improved.

Problems solved by technology

However, the conventional focal length adjustment apparatus configured as stated above has the following problems.

This makes the conventional focal length adjustment apparatus vulnerable to vibration in the case of unintentional falling or when an external shock is applied thereto.

The vulnerability in vibration disadvantageously increases a peak value in vibration at a resonance point, causing collisions between the holder 110 and other constituent elements.

This degrades the durability of the conventional focal length adjustment apparatus and also, excessively increases a response time for focal length adjustment (i.e. a time required to stop the movement of the lens.

Further, the above-described insufficient damping makes it difficult to control an accurate position of the holder 110, and to accurately adjust the focus of the lens received in the lens barrel 102, resulting in many problems to obtain vivid photographs or images.

Furthermore, when it is desired to mount a large number of lenses in the lens barrel 102, the holder 101 that is coupled with the lens barrel 102 is inevitably subjected to an increased load, requiring a great force for easy transfer thereof.

Increasing the amount of electric current to be applied to the coils 106, however, results in an increase in the consumption of electricity.

Also, raising the magnetic flux density requires to enhance the magnetism of the magnets 104, but the magnetism is a physical property value, and is difficult to vary.

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